740 Proc. roy. Soc. Med. Volume 69 October 1976 Most of the statistical information in this paper is from three sources: (1) Binnie W H, Cawson R A, Hilt G B & Soaper A E (1972) Oral Cancer in England and Wales: A national study of moribidity, mortality, curability and related factors. Office of Population Censuses and Surveys: Studies on Medical andPopulation Subjects No. 23, HMSO, London (2) Registrar General's Statistical Review of England and Wales. Part 1 - Tables Medical (Published annually) HMSO, London (3) Registrar General's Statistical Review of England and Wales. Supplement on Cancer HMSO, London (1968-70)

REFERENCES Ahlbom H E (1936) British Medical Journal ii, 331 (1937) Acta radiologica (Stockholm) 18, 163 Bionie W H (1975) In: Oral Mucosa in Health and Disease. Ed. A E Dolby. Blackwell, Oxford; p 301-334 Brown Kelly A (1919) Journal ofLaryngology 34,285 Cawson R A (1969) Proceedings ofthe Royal Society of Medicine 62, 610 Clemmesen J C (1965) Statistical Studies in the Aetiology of Malignant Neoplasms. Munksgaard, Copenhagen; 1, 59 Higgs J & Wells R S (1972) British Journal of Dermatology 86, Supplement 8, 88 Levin M L, Goldstein H & Gerhardt P R (1950) Journal ofthe American Medical Association 143, 336 Paterson D R (1919) Journal of Laryngology 34, 289 Pindborg J J (1971) Australian Dental Journal 16,83 Schwartz D, Lellouch J, Flamant R & Denoix P F (1962) Revue Frantais des Etudes Clinique et Biologique 7, 590 Smith J F (1975) Archives ofOtolaryngology 101, 276-277 Waldenstrom J & KIellberg S R (1939) Acta radiologica (Stockholm) 20, 618 Waldron C ATI97YIn: Thoma's Oral Pathology. Ed. R J Gorlin & H M Goldman. 6th ed. Mosby, St Louis; p 837-839 Wynder E L, Bross I J & Feldman R M (1957) Cancer 10, 1300

Dr N W Johnson (Department ofOral Pathology, London Hospital Medical College, London El 2AD)

The Role of Histopathology in Diagnosis and Prognosis of Oral Squamous Cell Carcinoma There can be little argument that histopathology plays a key role in cancer diagnosis, particularly in the mouth where access for biopsy is so easy. Techniques such as exfoliative cytology are notoriously unreliable, particularly when dealing with keratinized. mucosa, and will not be discussed further (for example, Folsom et al. 1972, Reddyetal. 1975). In spite of a somewhat variable clinical appearance, which may lead to doubt as to whether or not a suspicious lesion is really neoplastic, the majority of squamous cell carcinomas of the oral mucosa are readily diagnosable by conventional criteria on routine microscopic preparations: most are overtly invasive squamous cell carcinomas at presentation and the histopathologist can readily recognize them as such. Major difficulties do arise, however, in determining what are truly 'premalignant' lesions.

There occur in the oral mucosa, as in other mucosm, a range of keratotic lesions, some of which are clearly benign, others of which certainly presage invasive neoplasia. These are the range of conditions commonly and loosely known as oral leukoplakia - a word which has so many shades of meaning that it may be wise to abandon its use altogether. Whilst the chances of a patient with a keratotic lesion developing a carcinoma are much higher than in patients without such lesions, it must be remembered that the minority of oral cancers develop in pre-existing white patches perhaps of the order of 20% (see MacDonald 1975). Indeed, so-called leukoplakia is a much over-valued clinical sign of malignancy, and features such as erythroplakia, chronic ulceration and induration are much more sinister. Microscopically these white patches reveal a range from perfectly benign hyperkeratoses, through lesions showing variable degrees of epithelial atypia, to so-called 'carcinoma-in-situ', to 'micro-invasive carcinoma', to truly invasive neoplasms. This is the traditional battleground of the early diagnosis of oral cancer, but emphasis on it has acted for. many years to the detriment of detailed study of the variability of frank malignancies. This paper therefore reviews two major areas: (1) Methods for improving the accuracy and objectivity of diagnosis of the borderline case. (2) A consideration of the variability of overt invasive carcinomas, of prognostic features detectable therein, and of the value of these in the planning of patient management.

Methods for Improving the Objectivity and

Accuracy of Diagnosis ofPremalignant Lesions

At the cellular level squamous cell carcinomas show disturbances in the homeostatic mechanisms controlling cell division, cell maturation and cell aggregation. To these must be added evidence of host response seen in the tumour stroma, and the whole question of epithelial-mesenchymal interaction. Features attributable to each of these processes are listed in Table 1; some, of course, reflect disturbances in more than one of the fundamental control processes. Most attempts at measuring the degree of epithelial atypia in oral premalignant lesions relate to these signs, or to combinations of them, and some recent studies which have attempted to put this type of analysis on a more objective and quantitative basis are reviewed below. (1) Multifactoral analysis: Two studies deserve mention here. The first (Smith & Pindborg 1969) scores features objectively, but subjectively weights their importance. The second (Kramer et a!. 1970, Kramer et al. 1974), whilst involving more subjective scoring, calculates weighting factors in an entirely objective fashion.

Section ofOdontology with Section ofOncology and Section ofPlastic Surgery 741 Table I

Table 2

Disturbances in homeostatic mechanisms shown by

Features used to discriminate premalignant 'leukoplakia' (Kramer et al. 1970)

squamous cell carcinomas

Homeostatic mechanism Cell division

Signs

Cell maturation

Keratosis/parakeratosis 'Dyskeratosis' Irregular stratification Nucleolar alterations

Abnormal mitoses Mitotic activity Hyperchromatism Nuclear/cytoplasmic ratio Nuclear pleomorphism Anisonucleosis Hyperplasia/Atrophy

Abnormal mitoses in spinous layer Disturbed polarity of basal cells Abnormal mitoses in basal layer Hyperchromatism Russell bodies in lamina propria Enlarged nucleoli in spinous cells Cellular pleomorphism Intra-epithelial keratinizatfon

here is that known as discriminant analysis, in which two groups of cases are compared by Hyperplasia/atrophy asking the computer to calculate weighting factors Cell aggregation Intercellular space which produce maximum separation of the Acantholysis groups. Table 2 lists in order the eight most Pseudopodia Invasion important features used by the computer in Immune inflammatory response Stromal reactions making the discrimination between lesions which Vascularity became malignant and those which did not. Most Fibres Ground substance of these features have long been regarded as important, but the value of this type of study lies not only in confirming those features which do In the Smith & Pindborg system the severity of have prognostic significance, but also in removing 13 epithelial features is assessed by reference to from undue consideration features which seem of photographic standards, scored and weighted so little or no significance. Several other quantitative approaches for that an epithelial atypia index is arrived at for each biopsy. Indices thus determined have been assessing changes in homeostatic mechanisms in shown to correlate well with the progression to oral cancer and precancer should now be menmalignancy in chemically induced oral carcinoma tioned. Most of these are attempts accurately to measure a single feature. They have the advantage in rodents (MacDonald 1973). MacDonald & Rennie (1975) have used the over the foregoing of being strictly quantitative, system to score atypia in. three lesions which but the disadvantage of considering a single rarely if ever become malignant. From a total feature in isolation; the studies reviewed above possible score of 75 in the system, they obtained serve to emphasize the complex interrelation of a mean figures of 15 for denture-induced hyperrange of features in any diagnostic situation. plasia, 22 for lichen planus and 32 for squamous papilloma. Degrees of atypia are thus not un- (2) Measurement of nuclear changes: Measurecommon in benign lesions, and the question as to ment of the total nuclear DNA content of when a true premalignant score is reached sectioned or smeared cells, by quantitative microremains unanswered. Indeed, it would be naive photometry of Feulgen stained preparations, is to imagine that any sharp border exists. Studies often advocated (for example Cabrini 1973). A of this type are, however, valuable in assessing the sample of normal oral epithelium, or of lymphorelative importance of the features of atypia and cytes in the tissue, produces a narrow modal peak thus the weighting they should be given. For representing the DNA content of cells with theexample, keratinized cells below the normally diploid number of chromosomes. In hyperkeratinized layers, mitoses at an abnormally keratotic lesions there is a shift to higher values, superficial level in the epithelium and bizarre and carcinomas reveal a wide spread to the right mitoses were infrequent in this benign material, representing various degrees of polyploidy and perhaps suggesting these are features of atypia aneuploidy. However, a substantial proportion of lesions with quite marked atypia, and some overt particularly related to premalignancy. In the work of Kramer and colleagues 235 carcinomas, still show predominantly diploid biopsies of lesions subjectively diagnosed as values (Doyle & Manhold 1975). More extensive lichen planus, as benign keratoses, or as keratotic studies of this kind correlated with subsequent lesions with a degree of atypia were studied and behaviour of the lesion are required before the 13 overt carcinomas were added. Thirty-nine diagnostic value of Feulgen microspectrophotohistological features were scored on a semi- metry can be assessed. Precise counting of chromosome numbers and quantitative basis for each case, and the data subjected to a series of complex analyses with the a full karyotype analysis may also be performed, help of a computer. The approach of relevance but little or no work of this kind has been done on Nuclear/cytoplasmic ratio Cell pleomorphism

742 Proc. roy. Soc. Med. Volume 69 October 1976

oral cancer. There is some evidence that, with uterine cervix, the spectrum from dysplasia to carcinoma-in-situ to overt carcinoma shows progressive increases in polyheteroploidy, but there is considerable variation so that although statistically significant differences are found between the groups when a large number of cases are studied (Kirkland 1966) individual cases cannot be confidently assigned. Very few tumours have consistent marker chromosomes detected as abnormal karyotypes by features such as length or centromere position (Wakonig-Vaartaja & Hughes 1967). By the use of stereologic point counting techniques it is possible accurately to measure nuclear-cytoplasmic ratio in either paraffin or plastic-embedded sections. Studies in developing hamster cheek pouch carcinomas show, for example, a progressive rise in this ratio from about 0.5 to 1.0 or more as the tissue moves from normal through hyperplastic and papillomatous phases to carcinoma (Franklin 1974). Taken alone, however, such measurements can never hope to be of diagnostic value because similar changes are also associated with other causes of increased cell proliferation, e.g. in wound healing. (3) Changes in the cell surface: Similar stereologic quantitation of desmosome and hemidesmosome numbers and sizes have been performed in electron micrographs (e.g. MacDonald 1973, White & Squier 1974). In experimental carcinogenesis in animals, the proportion of the cell membrane of basal oral epithelial cells occupied by attachments is significantly decreased once malignancy is established. Again, however, these figures are of limited value in isolation, because they are not unique to neoplastic disease, occurring in a number of specific bullous diseases and even in nonspecific inflammation. Likewise ultrastructural studies of breaks in the epithelial basal lamina and the extension through them of pseudopodia from basal epithelial cells are an early sign of invasion, but are not unique to neoplasia (Frithiof 1972, Smith 1972a, Tarin 1972). Nor are these changes readily quantifiable: breaks occur in inflammation and pseudopodia in other hyperplastic conditions. Apart from the possible development of tumour-specific antigens (Cannell 1974, Kennedy 1975), the expression of other cell surface antigens may be altered in malignancy. It has been shown by Dabelsteen & Pindborg (1973) that blood group antigens A and B are lost from the surfaces of oral prickle cells in carcinoma and that there is partial loss in premalignant lesions (Dabelsteen et al. 1975). Similar changes have been found in uterine cervix (Davidsohn et al. 1969) and it has been suggested that this phenomenon may be used as an early diagnostic test. The system can be made

quantitative by determining the end-point titre with immunofluorescence of immunoperoxidase techniques. However, there is a wide individual variation in normal levels so that control healthy mucosa must always be taken fronm the same patient, and once again this loss of antigenic expression is not unique to neoplastic processes; it occurs for example in migrating epithelium during wound healing (Dabelsteen & Fejerskov 1974). (4) Epithelial cell proliferation rates: There is good evidence that the uptake of tritiated thymidine by epithelial cells of the uterine cervix incubated with isotope in vitro - alters markedly and significantly from normal, through squamous metaplasia, and increasing degrees of dysplasia, to carcinoma-in-situ (Rubio & Lagerlof 1974). Not only does the labelling index rise from a mean of 7 % of the cells present in normal tissue to 35 % in carcinoma-in-situ, but the distribution of labelled cells comes progressively to involve all epithelial layers right through to the surface. A few cases exist in which the density and distribution of labelling is more extensive than the histology would indicate, and it is tempting to suggest that these are already severe lesions in terms of biological activity. Relatively little work of this kind has been conducted on oral premalignant lesions. In vitro 3H-thymidine labelling of keratotic lesions compared with control normal mucosa from the same mouths has shown a doubling of the labelling indices for the lesions - in terms of the proportion of nucleated cells rising from approximately 3 % to approximately 6 % and, therefore, approximately halving the tissue turnover time (Alvares et al. 1972, MacDonald & Warnakulasuriya 1976). Unlike in uterine epithelium, however, labelled cells were restricted to the three cell layers closest to the basement membrane. ElLabban et al. (1971) counted the mitotic activity in oral keratoses and found higher values than normal, with many more supra-basal cells involved. However, many factors such as site of lesion, age, time of day and degree of inflammation all influence the results of cell kinetic studies and much more work of this kind is necessary before its diagnostic value can be assessed. Again, also, it must be remembered that alteration in cell proliferation by no means completely characterizes the neoplastic process.

(5) Histochemical/biochemical alterations: Most of the available data relate to respiratory enzymes. A relatively high glycolytic metabolism is a wellknown feature which distinguishes malignant tissue from its tissue of origin - part of the phenomenon of biochemical convergence - and

Section ofOdontology with Section ofOncology and Section ofPlastic Surgery 743

oral cancer is no exception. Consistent with this is the finding that electrophoresis of homogenates of oral keratoses show a cathodic shift in LDH iso-enzymes (Langvad & Roed-Petersen 1970). A decrease in succinic dehydrogenase activity and an increase in glucose-6-phosphate dehydrogenase (G6PD) activity occurs in premalignant and malignant oral epithelium, reflecting a shift from Krebs cycle activity (Cabrini 1973). Recently the increase in G6PD activity has created a great deal of interest. This is a key enzyme in the pentose phosphate shunt which is of potentially great importance in malignant tissues because the pathway provides NADPH required for biosynthesis of cell structure and provides pentose sugars needed for nucleotide synthesis, both of which are active processes in neoplasms. Butcher (1975) has shown that, provided the appropriate tetrazolium salt is used as histochemical reagent, this increased activity is totally abolished, with healthy bronchial epithelium, by the presence of oxygen in the incubation medium. With carcinoma of the bronchus there is no oxygen inhibition and a strong 'all or none' demonstration of malignant cells is possible. Heyden and collaborators have confirmed this with oral, skin and vaginal cancer, and have shown in oral premalignant lesions the presence of isolated cells with this 'atypia of oxidative metabolism' (Heyden 1974). It is thus possible that the method may detect a transformed malignant cell before it is recognizable by conventional morphological criteria, but we do not yet know whether these striking changes are unique to malignant cells. So far as hydrolytic enzymes are concerned Smith (1972b) has shown, both in hamster cheek carcinogenesis and in human premalignant lesions, a progressive build up in large deposits of lysosomal enzymes in basal epithelial cells and in macrophages in the upper part of the lamina propria. These changes usually precede microscopic atypia and may provide an early warning system - though they have not yet been put on a quantitative basis.

(6) Stromal response: Few data are available on this important aspect apart from the inclusion of some connective tissue features in the study of Kramer et al. (1970, 1974) referred to above. Lehner (1969) has shown that the round cell infiltrate beneath oral epithelium increases progressively from benign keratoses through varying degrees of atypia to carcinoma: pyroninophilic cells are particularly involved, possible responding to new antigentic determinants on malignant cells. A marked macrophage infiltration is also associated with the final development of malignancy in experimentally produced hamster cheek carcinoma (Gohari & Johnson 1974).

Prognostic Features of Overt Malignancies (1) Clinical grading and staging: A number of variations of the basic TNM staging system recommended by the International Union against Cancer (e.g. Union Internationale Contre le Cancer 1974, Spiessl et al. 1973) have been used for oral cancer, and all of these have strong correlations with survival. They are thus of value ir determining how radical the initial therapeutic approach should be and such data should be assembled on all cases in each treatment centre. The histopathologist can help here by assessing depth of infiltration from his biopsy, and thus refining the T grade, and, if the opportunity presents, by confirming the presence or absence of neoplasm in regional lymph nodes. (2) Microscopic grading of tumour type and differentiation: Nobody would doubt the prime importance of knowing tumour type, from histology, before planning treatment. For example, mucosal squamous cell carcinomas behave differently from salivary gland neoplasms and, within these latter, the behaviour of, say, an adenoid cystic carcinoma is very different from that of a pleomorphic adenoma. What is less well understood, and of unproven value, is an assessment of variations in the detailed tissue structure of different squamous cell carcinomas of the mouth. It is a widely held view that poorly differentiated, or anaplastic, carcinomas are more aggressive, i.e. they infiltrate more rapidly and more widely and metastasize earlier than well-differentiated neoplasms with consequent implications on patient survival time. Since the original work of Broders (e.g. Broders 1941) a number of grading schemes have been proposed but they have never been adequately tested on oral malignancies. Some useful indicators are, however, available in the literature from carcinomas at other sites but, before looking at some of these, we should examine some features of host response visible in the biopsy - particularly the nature and intensity of the local immune inflammatory response visible in the stroma - because there is increasing evidence that this is at least as helpful in determining tumour behaviour as are details of the epithelium itself.

(3) Stromal response: Excluding as far as possible inflammation subsequent to trauma or ulceration, oral squamous cell carcinomas show a wide variation in the inflammatory response they evoke. This ranges from the dense lymphocyte/ macrophage infiltrate beneath verrucous carcinoma (Fig 1) - which for all practical purposes does not invade - to complete absence of inflammatory cells surrounding the deeply infiltrative advancing front of many squamous carcinomas (Fig 2). In between there are varia-

744 Proc. roy. Soc. Med. Volume 69 October 1976

Fig 1 Verrucous carcinoma of buccal mucosa in man aged 70. There is a dense subepithelial immune inflammatory response in which lymphocytes and macrophages are prominent. H & E. x 80

Fig 3 A moderately dense cellular inflammatory response surrounds the advancing front, and extends into the tumour stroma, in this invasive carcinoma of floor of mouth in a 71-year-old woman. Most are mononuclear cells; in this case a striking number of eosinophils also were present. H & E. x 80

Fig 2 Advancing front of a squamous cell carcinoma ofretromolar area in a man aged 49. The muscle is infiltrated and there is complete absence of inflammatory response. H & E. x 80

Fig 4 Advancing front of carcinoma ofpalate in man aged 64. There is a light inflammatory infiltrate around the tumour, which extends a short distance into the tumour stroma. H & E. x 80

tions in the intensity of infiltration and in its proximity to the neoplastic cells (Figs 3 & 4). It is clearly of great interest to know whether these immune-effector cells are actually controlling the progression of the lesion. Evidence that this is so has appeared periodically since the pioneering work of Black and colleagues in the 1950s, dealing with both breast and gastric carcinomas (e.g. Black et al., 1955, Black et al., 1975). They found that increasing degrees of tumour cell differentiation, lymphoid infiltrate, and degree of sinus histiocytosis in regional lymph nodes were additive and strongly positively correlated with favourable five-year survivals - independent of patient age and the presence or absence of lymph node metastases. Similar data are now available for skin - particularly melanoma (e.g. Cochran 1969) and ovarian tumours (e.g. Barber et al. 1975) although in the latter the inflammatory infiltrate is of less value.

Attempts at examining the relationships in the mouth have been few. Jones & Coyle (1969) took 50 carcinomas of the lower lip, 25 of which metastasized, and 25 which did not, and found that lack of differentiation, poor lymphocytic response and mucoid change in the stroma were signs of poor prognosis. In terms of a crude assessment of round cell inflltration Paavolainen et al. (1973) in Finland found a similaK relationship in tongue cancer. On the basis of combining subjective scores for three features of the tumour cell population and three of the tumour-host relationship, Willen et al. (1975) showed strong correlations between total scores and patient survival with gingival cancer. Similar approaches with similar results have been reported for palate (Eneroth & Moberger 1973). Recently Noone et al. (1974) showed strikingly increased survival with oral cancer when the primary was heavily inflltrated with inflammatory cells.

Section of Odontology with Section of Oticology and Section ofPlastic Surgery 745

(4) Tumour cell proliferationi rates - stiudies of cell kinetics: As continued epithelial cell proliferation is one of the fundamental featuires of carcinomas, it may be thought that sophisticated studies of the cell kinetics would produce helpful prognostic data. The number of mitoses observed is a standard component of most histological grading systems though, as described below, this did not appear of significance in our own recent work. There is certainly a large literature on mitotic activity in neoplasms, including sophisticated cell cycle analyses using tritiated thymidine administered in vivo, or by incubation of biopsies with isotope in vitro. Whilst this work has told us much about the range of abnormalities which exist in neoplastic tissues, there seem to be no proven prognostic uses yet. Indeed the length of the phases of the cell cycle in squamous carcinoma may not be strikingly different from those of normal squamous cells; because there are certainly very many dividing cells, the degree of cell death must also be increased or tumours would enlarge much more rapidly than they in fact do (see, for example, Baserga 1971). The extensive studies by Glucksmann (1965) on the relation between the histology of skin, uterine cervix and oral carcinoma and response to radiotherapy are important. These dispel the generalization that anaplastic carcinomas respond well to therapy, and well-differentiated tumours respond poorly. Indeed the reverse may be true, probably because there are fewer cells in the dangerous progenitor compartment to be disposed of, postmitotic cells being, of course, of no danger to the host. This work furthermore shows that the initial histological response of the primary tumour to radiotherapy is of prognostic value: if the effect of treatment is to increase the number

Table 3 Significance of epithelial features (X2 analysis)

EpithelialJeatures

P

of keratinizing, maturing cells, the response is favourable. Conversely, the persistence of unchanged reproductive cells, whether dividing or not, is sinister - and it is these, rather than bizarre cells, abnormal mitoses, and degenerate cells which indicate the likelihood of resumed tumour growth. Such findings should, therefore, form a basis for selecting patients with apparently refractory tumour for subsequent surgical treatment. Likewise the effect of radiation on mitotic activity has been shown to be of prognostic value in gynecological tumours and might more regularly be used to monitor and plan treatment. The initial response to both high therapeutic doses (e.g. Atkin 1960, Cox et al. 1965) and to low test doses of the order of only a few hundred rad (Wakonig-Vaartaja & Hughes 1967) seems meaningful. More variable results have been obtained with oral cancer (e.g. Friedman 1973, Tubiana et al. 1975).

(5) Mttltifactorial analysis: The studies so far mentioned have chosen to score and evaluate a small number of the histological features present in the biopsies. Some of these seem to be independent variables, many other features are ignored, and it is not really known which are the most significant and the degree to which they interact. Accordingly we recently mounted a study designed to relate these and other histological features of oral squamous cell carcinoma to prognosis, using a computer to aid analysis of our findings. One hundred cases were selected from the files of the Department of Oral Pathology, London Hospital Medical College, in all of which there was adequate clinical information available, including at least five-year follow up, and for which adequate histological material was available from the original diagnostic biopsy. A total of 39 histological features, 23 for the epithelium and 16 for the stroma, were scored on a semi-

Stratification of invading epitheliuim ,< 0.025 Thickness of surface epithelium overlying tumour. Space between

0.100-0.250

Table 4 Significance of connective tissue features x2 analysis)

basal cells in tumour. Nuclear

cytoplasmic ratio of tumour cells

P Connective tissue features Individual epithelial cells in stroma

< 0.025

Inflammatory infiltrate within tumour

< 0.050

Prickle cell nucleoli size and staining. Basal cell nucleoli staining and size. Basal cell hyperchromatism. Bridges between prickle cells

0.250-0.500

Macrophages. Vascularity

0.100-0.250

Space between prickle cells in ttimour.

0.500-0.750

Polymorphonuclear leukocytes. Russell bodies. Fibrosis around tumour. Inflammatory infiltrate around tumour. Plasma cells. Eosinophils

0.250-0.500

0.750

Loose connective tissue around or within tumour mass. Lymphocytes

0.500-0.750

-

-

Individual cell keratinization number. Prickle cell hyperchromnatism. Prickle cell nucleoli number -

Basal cell nucleoli number. Pleomorphism of tumour cells. Anisonucleosis. Bridges between basal cells in tumour. Mitotic activity. Keratin pearls -

>

Epithelial-infiltrate distance. Mast cells. Fibrosis within tumour mass

> 0.750

746 Proc. roy. Soc. Med. Volume 69 October 1976 This raises the controversy as to whether or not quantitative basis and analysed for their association with five-year survival, the strength of the prophylactic removal of nodes is desirable; once tumour is clinically obvious in a regional node association being determined by a x2 test. The results are summarized in Tables 3 and 4 there can be little doubt that node dissection or which rank the epithelial and connective tissue irradiation is necessary, for one of the most features studied. The only epithelial feature which helpful things we can do to aid the body's reached statistical significance was the regularity immunological defences against a neoplasm is to of stratification of the invading malignant epi- reduce the tumour burden. Prophylactic disthelium; progressive loss of stratification corre- section or irradiation is a different matter, howlated with lower chance of five-year survival in ever, and the view that these procedures inhibit the important local immune defences is perthe initial analysis. Of the connective tissue features, the presence suasive, although even with breast cancer, where of individual epithelial cells in the stroma, an there is much more data, the results are equivocal. indication of diffuse infiltration, showed a sig- So far as oral cancer is concerned we do not yet nificant negative correlation with survival. The have sufficient data to draw conclusions and the other significant feature was the intensity of the literature contains conflicting evidence (see local immune inflammatory response, which was Lawrence et al. 1974, Million 1974, McKelvie 1976, Stell & Green 1976). positively correlated with survival. When mathematically corrected for the independent effects on survival of age, sex, site and Relationship to Treatment size of lesion, the intensity of the inflammatory In conclusion, what does all this research point infiltrate, the presence of macrophages within this to in the way of practical help in the management infiltrate, and the numbers of individual epithelial of individual patients? Three things can perhaps cells in the stroma were the only parameters to be said: (1) If, from the type of studies of tumour reach statistical significance. It is of particular structure and host response described, we could interest to note that some of the epithelial features, predict more accurately the'degree of malignancy including keratin production and mitotic activity, of a given tumour, much would be gained. Cases classically given great weight in grading systems, scoring low malignancy points could happily be were of no prognostic significance in this analysis. treated conservatively - those with high points So far we, and almost all other authors, have being attacked more freely by radical surgery, tried to make correlations with survival. This is, extensive radiotherapy or chemotherapy - or by of course, of limited value in searching for differ- combined treatment. (2) If the relation between ences in the behaviour of different tumours radiotherapy and chemotherapy on the one hand, because the object of treatment is to minimize and the proliferative activity, and histological such differences - by curing all patients. Thus differentiation of the tumour, and intensity of correlations with lymph node involvement, with local immune response on the other were better depth of infiltration, rate of growth, frequency of understood and sequential biopsy during treatprimary recurrence and so on, must also be made, ment more widely applied, optimum dose regimes and it is in this way that analysis of our data is may more easily be determined. (3) Large-scale surveys using combined clinical, histopathoproceeding. logical and immunological skills are necessary to (6) Changes in local lymph nodes: That regional solve the question of whether or not prophylactic lymph nodes exert an inhibitory effect on tumour block dissection of the neck helps the patient. It is hoped that this review may help to stimuprogression is now well established. The correlation of sinus histiocytosis with improved late further work and further cooperation in each prognosis of breast cancer referred to earlier is of these directions. one kind of evidence (see e.g. Hunter et al. 1975). REFERENCES Lymphocytes derived from regional nodes are Alvares 0, Skougaard M R, Pindborg J J & Roed-Petersen B (1972) Scandinavian Journal of Dental Research 80, 510-514 much more responsive to tumour extracts, as well Atkin Lancet ii, 778-781 as to nonspecific mitogens, than those of peri- BarberNHBR(1960) K, Sommers S C, Snyder R & Kwon T H (1975) Anierican Journal of Obstetrics & Gynecology 121, 795-807 pheral blood (e.g. Ellis et al. 1975). Baserga R ed.(1971) The Cell Cycle and Cancer. 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Mr E J Shillitoel (Departmenit of Oral Immunology and Microbiology, Guty's Hospital Medical and Dental Schools, Lonidon SEI 9RT)

The Role of Immunology in the Diagnosis, Prognosis and Treatpent Planning of Oral Cancer The scientific study of tumour immunology began when inbred strains of histocompatible animals first became available. Prehn & Main (1957) showed that when a malignant tumour was transplanted from one animal to another it was rejected, although normal skin from the same donor was readily accepted. This indication of tumour-specific immunity led to the study and demonstration of the complex immune responses to tumours. Many factors have been elucidated first in animal models and then applied to man, so that the study of animals usually precedes advances in man.

Nonspecific Immuiilological Defects in Cancer It is well established that patients with malignant tumours have depressed immune responses, particularly of cell-mediated immunity. The capacity to develop a delayed hypersensitivity response to contact sensitizing agents such as di-nitro-chlorobenzene (DNCB) is progressively impaired as tuimour growth progresses. Eilber & Morton (1970) demonstrated that in a group of 100 patients with various forms of advanced malignancy only 60% could be sensitized to DNCB, compared to 95 % of healthy control subjects. Of the patients who were sensitized, 92 % remained tumour free six months later, whilst of those who could not be sensitized, 93% had distant metastases or had died. The inability to develop sensitization was therefore associated with a poor prognosis and could have been used to predict the patient's progress with some accuracy. However, delayed hypersensitivity skin testing is an imperfect form of assessment and has not gained acceptance as a routine clinical procedure. Of the patients who were sensitized to contact sensitizing agents a certain proportion might later develop recurrent or metastatic tumours but this could not be predicted in advance by skin tests. Retesting with the same agent can demonstrate whether or not sensitization has been retained and this might be important, as a loss of response to common microbial antigens has also been associated with poor prognosis (Eilber & Morton 'Address for correspondence: Department of Microbiology, Milton S Hershey Medical Centre, Hershey, Pennsylvania 17033, USA